Why CO2 is Irrelevant to the Earth’s Lower Atmosphere; You Can’t Absorb More than 100%

The one thing I’ve learned about Climate Science is that the “experts” do everything to avoid the actual science supporting the Greenhouse Gas Effect. To isolate the impact of CO2 on the climate one must understand the physics of the CO2 molecule and the thermodynamics of the atmosphere.

This is the radiative profile of the CO2 molecule. Note the -80 Degree C and 15 micron peak in the following graphic.

CO2’s only defined mechanism by which to affect climate change is through the Greenhouse Gas Effect and the thermalization of longwave IR between 13 and 18 Microns, with a peak of 15 Microns. Every observation much be related back to that single mechanism for CO2 to be the cause.

Energy is transferred through the atmosphere by three mechanisms; Conduction, Convection and Radiation. Conduction and convection dominate the warm water vapor rich and dense lower atmosphere. Radiation dominates the upper atmosphere.

Because the lower atmosphere is tightly packed, kinetic energy is easily passed from one molecule to the other. The radiative path is also very short relative to other altitudes, meaning that the molecules can momentarily “trap” more radiation resulting in warming. That is why high levels of water vapor in the lower atmosphere is so important. Water vapor traps and converts huge amounts of outgoing longwave radiation into thermal kinetic energy.

At higher altitudes, the molecules have wide separations representing large windows for radiation to easily pass. That is why CO2 works to cool the stratosphere. A molecule in the stratosphere radiating towards earth is radiating into a traffic jam, with an increasing number of radiation absorbing molecules in its path the closer it gets to earth. It is unlikely that the radiation from a stratospheric molecule will be able to pass the gauntlet of ever-increasing molecules and smaller and smaller windows to get to earth. On the other hand, a stratospheric molecule radiating towards outer space is facing the opposite of a traffic jam, with the spacing between cars increasing the farther away it gets, and the windows keep getting bigger and bigger. That is why radiation is best for cooling, not warming. It most efficiently transfers heat out of the atmosphere and it does it near the speed of light.

The earth emits radiation centered around 9.5 to 10 microns, or about room temperature. CO2 thermalizes radiation between 13 and 18 microns, which is consistent with a black body of temperature between -50 and -110 degree C. CO2 absorbs the far right (cool end) of the IR spectrum emitted by the earth.

With that understanding, we can then examine CO2’s role is altering the earth’s lower atmosphere’s temperature. To do that we need to look at a “gas cell” filled with various amounts of CO2, and then shine a light of 13 thru 18 microns into it and measure its absorption.

We will start with the pre-industrial CO2 level of 280 ppm. What we find is that at that concentration, 100% of the longwave IR radiation between 13 and 18 microns is absorbed by the altitude of 150 cm, or about 5 feet. 13 and 18 microns with a peak of 15 microns has a wave number of 666 in the following graphic. The peak reaching 1 represents 100% absorption, or 0% transmission. The take home is that by an altitude of 5 feet, the pre-industrial CO2 Greenhouse Gas Effect is saturated.

Now we have to measure the change in the saturation altitude to understand the impact of the additional 130 ppm of CO2 added to the atmosphere since the start of the industrial age. This literally is the only effect CO2 has on changing the climate. Once again, you can’t trap more than 100%, and pre-industrial CO2 saturates by 5 ft. All CO2 can do by increasing its concentration is to make the radiative windows smaller so that the outgoing radiation gets “trapped” sooner (closer to earth).

What do we find when we change the gas cell to today’s CO2 level of 410 ppm? We find that 100% saturation occurs at 120 cm, or about 4 feet. That literally is the only relevant contribution the post-industrial CO2 makes to the climate. Saturation occurs 1 foot closer to the earth.

Another way to look at it is to plug in 280 ppm for the saturation level of 410 ppm to see how much less radiation is being trapped. As you can see, about 98% of the radiation is being absorbed by 4 feet, and the remaining 1 foot absorbs the final 2%. That is it, that is the contribution of post-industrial CO2 and you are being told that that small change can cause catastrophic climate change.

In reality, that slight change is completely immaterial because the lower atmosphere is so well mixed through conduction and convection, minor changes in the saturation level are irrelevant. Take a thermometer outside and measure the temperature at 4 ft and then again at 5 foot and you will record identical temperatures. Once again, CO2 doesn’t trap more heat, it simply traps the heat sooner. You can’t trap more than 100%. That is why all these claims of CO2 causing catastrophic climate change are complete and utter nonsense.

Additionally, remember, the above example isolates the impact of CO2. It is a minor trace Greenhouse Gas, with a very narrow absorption band. Just look at the absorption spectrum of all Greenhouse Gasses, and the breadth of what water vapor absorbs, and you quickly realize this focus on CO2 is completely absurd. Additionally, water vapor also absorbs longwave IR radiation between 13 and 18 microns. It just saturates at a higher altitude.

If we decide to look not only at the impact of CO2, but the entire atmosphere including water vapor, the impact of CO2 is simply drowned out by water vapor and other factors. If, using 280 ppm CO2, we program MODTRAN to be looking down from 0.01 km and measure the Upward IR Heat Flux, we get 446.508 W/m2.

This is the IR Profile of the pre-industrial lower atmosphere.

If we then change only the CO2 level from 280 to 410 ppm to reflect the marginal impact of industrial era CO2, we discover that the change in Upward IR Heat Flux is a whopping 0.00 W/m2. There is absolutely no change what so ever to the lower atmosphere with the addition of 130 ppm industrial CO2. None, nada, zip, the Upward IR Heat Flux remains completely unchanged at 446.508 W/m2.

I have yet to find an atmospheric calculator, modeler or Meteorology textbook that shows that CO2 has any impact at all on the atmosphere. Only when you get into the Climate Science Department does CO2 suddenly play a significant role in the climate, and their models are completely worthless.

Much has been written about CO2 causing the Sea Ice to decline. Al Gore claims melting glaciers will flood Manhatten. The only problem is, the LWIR emitted by CO2 won’t melt ice. Longwave IR between 13 and 18 microns has a black body temperature of -80 Degree C. The graphic of the Spectralcalc output is above. The blackbody radiation of 0.00 Degree C Ice has a peak radiation of 10.5 microns. In other words, Ice emits higher energy radiation than CO2 does (shorter wavelength radiation has higher energy). That isn’t a joke. Climate alarmists claim that energy that won’t even melt ice can cause catastrophic global warming. Sorry, climate change.

In conclusion, either the SpectralCal and MODTRAN Programs are lying to me, or the Climate Scientists are, and I tend to trust the calculators.

Honest Liberty, thanks for the comment and the interest. The only defined mechanism by which CO2 can affect climate change is through the Greenhouse Gas Effect. The Greenhouse Gas Effect is when a Greenhouse Gas absorbs a particular wavelength of longwave IR radiation and “thermalizes” it. It changes electromagnetic radiation into kinetic or thermal energy. Thermometers measure kinetic energy in the atmosphere. CO2 only thermalizes a very very very narrow band of LWIR, between 13 and 18 microns, peak of 15. The earth radiates between 10 and 9.5 microns, and ice radiates around 10.5. In other words Ice emits higher energy radiation than CO2. While the earth certainly does emit 15 micron wavelength, it is important to understand that that is way to the right (cold) end of the spectrum. CO2 doesn’t warm anything, it prevents things from falling below -50 deg C. You can see that in the stratosphere which doesn’t fall below that level. Hope that helps.

“Energy is transferred through the atmosphere by three mechanisms; Conduction, Convection and Radiation.”

This is incomplete. There are four mechanisms, if one takes the ‘conduction’ to mean transfers of thermal energy between molecules. The fourth is conduction from the surface directly to the atmosphere without radiative heating.

As the GHG concentration is reduced, the importance of the contact with the surface increases. First, the heating of the surface by the sun increases as the GHG’s get out of the way. Second, as the heating by the surface increases, the ability of the atmosphere to dispose of heat by IR radiation decreases. When the GHG concentration reaches zero, the surface would heat the air with approximately twice as much energy as is does now (it would rise to about 330 W/sq m), and the atmosphere would have no ability to dispose of that heat save back to a cool surface at might.

In that condition thermal equilibrium would be achieved only above 100 degrees C. Atmospheric temperature discussion is dominated by talk of radiation on the basis that without GHG’s, the atmosphere would be very cold, like the surface of the moon. The surface of the moon and an atmosphere are not comparable at all. As GHG’s approach low values, the global average temperature will rise rapidly.

Yes, the radiative contribution to the warming will drop to zero, but that is not the only direct cause of heating. This whole thing needs a rethink.